Hi IanS,
Welcome to the Mattress Forum! I’m sorry to hear of your neck issues, but I’m happy that you’ve found a pillow that assists with your pain.
A topper can be a very effective alternative to purchasing an entirely new mattress, especially when your current bed is brand new and provides good support, and is simply something that has become a bit too firm for your current comfort needs.
A latex toper can be a comfortable choice to provide a bit of extra plushness, but also something that provides a bit of support. Latex has an unusual combination of surface softness and deeper firmness/support that comes from its elasticity, it’s point elasticity (ability to conform to the shape of a body) and its compression modulus (the ability to get firmer faster with deeper compression than other types of foam). This means that it can enhance the pressure relieving layers above it because of its surface softness and point elasticity but it is also very supportive and can “stop” the heavier parts of the body from sinking in too deeply. It is also very resilient (it returns a high percentage of the energy of compression instead of absorbing it like memory foam which has very low resilience) so it can enhance the “feel” of the mattress by making it more responsive and more adaptable to different body profiles and sleeping positions rather than the less responsive feeling of memory foam or the stiffer and less adaptable characteristics of polyfoam. Latex is also a very durable material (it’s the most durable of all the foam types) so it can add to the durability of a mattress compared to other materials but the deeper layers of a mattress have less effect on mattress durability (a mattress will soften and break down from the top down) and more of an effect on performance and support/alignment so this would be less of a factor in its use. Whether or not you would like the feel of a latex topper of course would ultimately come down to your own personal testing, as the overall comfort will be determined by the topper along with the mattress upon which it is placed.
There is an excellent post about toppers, including a few posts that it links to, in post #2 here.
There is also a post here listing some of the toppers of which I am aware that can be returned.
The topper post I linked to above will discuss some of the other styles of toppers (polyfoam, natural fibers, microcoils…), but in your situation your thought of using latex would certainly be a very logical choice.
Phoenix